Stove

ABSTRACT

A stove has a fuel reservoir which communicates via fuel supply line with a burner. A stop valve in the fuel supply line controls fuel supply from the fuel reservoir to the burner. A normally-open emergency shut-off valve in the fuel supply line is operable to close the fuel supply line if the fuel pressure rises a preset amount above a normal operating pressure due to overheating of the fuel reservoir for example.

INTRODUCTION

This invention relates to stoves, and in particular to chafing burnersand the like.

The invention is particularly concerned with compact portablefreestanding stoves of the type used in the catering industry and alsofor leisure activities, such as camping, hiking, sailing and the like. Astove of this type is described in PCT Patent Application PublicationNo. WO2008/119796, which discloses a stove having a burner, a fuelreservoir, a fuel supply line communicating between the fuel reservoirand the burner, a stop valve in the fuel supply line which is operableto control the supply of fuel from the reservoir to the burner, and anormally open emergency shut-off valve which is operable to close thefuel supply line, when the stove is tipped away from a normal upstandingoperating position by a preset amount. This provides a safety cut off offuel gas supply to the burner if the stove is accidentally knocked over.Because of the proximity of the burner to the fuel reservoir, andparticularly when the burner is used for extended periods, some of theheat generated at the burner may cause heating of the reservoir, with aconsequent increase in pressure in the fuel gas contained therein. Thisis undesirable from a safety point of view and also presentsdifficulties in regulating the temperature produced by the burner andpossible overheating and spoiling of the foodstuffs being heated by theburner in use. There is also the possibility of damage to the burner andthe food display unit.

The present invention is directed towards overcoming these problems.

SUMMARY OF THE INVENTION

According to the invention, there is provided a stove, including:

-   -   a burner,    -   a fuel reservoir,    -   a fuel supply line communicating between the fuel reservoir and        the burner,    -   a stop valve in the fuel supply line which is operable to        control the supply of fuel from the fuel reservoir to the        burner, and    -   a normally open emergency shut-off valve in the fuel supply line        which is operable to close the fuel supply line,    -   characterised in that said emergency shut-off valve is operable        to close the fuel supply line in response to the fuel pressure        in the fuel supply line, when said fuel pressure reaches a        preset excess fuel pressure above a preselected normal operating        fuel pressure.

Thus, advantageously, the stove of the invention will automatically shutdown if the fuel reservoir is overheated causing the pressure of thefuel contained therein to be increased by an undesirable amount.

In one embodiment of the invention, the emergency shut-off valveincludes:

-   -   a valve housing having a through bore,    -   a complementary valve plunger slidably mounted in the bore,    -   said valve plunger being movable relative to the bore between an        open position and a closed position,    -   said valve plunger cooperating with the bore such that, in the        open position, a fuel passage through the bore is provided and        in the closed position, fuel flow through the bore is prevented.

In another embodiment, the bore has a bore fuel inlet communicating withthe fuel reservoir,

-   -   the plunger has a fuel passage extending through the plunger        with a plunger fuel inlet and terminating in a fuel outlet        nozzle,    -   said plunger fuel inlet being provided at a side wall of the        plunger which slidably engages the bore,    -   resilient seals being provided at each side of the plunger fuel        inlet which are engagable between the plunger and the bore to        prevent through passage of fuel between the bore and the        plunger,    -   a bypass recess in the bore which cooperates with the plunger to        allow fuel to bypass the resilient seal located between the        plunger fuel inlet and the bore fuel inlet when the plunger is        in the open position.

In a further embodiment, retaining means is provided for retaining thevalve plunger in the open position, when the fuel pressure is below saidpreset excess fuel pressure.

In another embodiment, the retaining means comprises a resilientpressure ring mounted in a circumferential recess in the plunger andfrictionally engaging with the bore.

In another embodiment, the retaining means projects outwardly of theplunger for engagement within an associated annular groove in the borewhen the plunger is in the open position.

In another embodiment, the retaining means is a spring mounted in thevalve housing and engaging and urging the plunger towards the openposition.

In another embodiment, a fuel filter is mounted within the fuel passagein the valve plunger.

In another embodiment, a cap is mounted at an outer end of the throughbore, said cap being engagable with the valve plunger when said valveplunger is at the outer end of the through bore to retain the valveplunger within the through bore, said cap having an opening therein inalignment with the fuel outlet nozzle to allow through-passage of fuelgas discharged from the nozzle in use.

In another embodiment, the valve plunger comprises an inner part and anouter part joined by a threaded connector, a lower end of the outer partforming a male threaded connector for engaging with a complementaryfemale threaded socket formed at an upper end of the inner part, saidrecess for reception of the pressure ring being formed between saidparts when they are engaged.

In a further embodiment, the stop valve comprises a valve body mountedat a top of the canister, the valve housing of the emergency shut-offvalve having an outer threaded portion in screw engagement with acomplementary threaded bore in the valve body, a valve head at a lowerend of the valve housing being engagable with an associated valve seatformed at an inner end of the bore at an outlet end of a fuel inletopening communicating with the fuel reservoir.

In another embodiment, said bore is stepped having an enlarged threadedouter portion which receives the valve housing and a smaller diametersmooth bored inner portion, the fuel inlet opening being formed by aport at an inner end of said inner portion, a seal being mounted in anassociated circumferential groove at a lower end of the valve housingsealingly engaging between the valve housing and a wall of the innerportion above the bore fuel inlet in a gas-tight manner to ensure fuelgas must pass through the bore fuel inlet.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more clearly understood by the followingdescription of some embodiments thereof, given by way of example only,with reference to the accompanying drawings, in which:

FIG. 1 is a sectional elevational view of a stove according to theinvention;

FIG. 2 is an enlarged detail sectional elevational view of an emergencyshut-off valve assembly forming portion of the stove, shown in an openposition;

FIG. 3 is a view similar to FIG. 2, showing the emergency shut-off valvein a closed position; and

FIG. 4 is a view similar to FIG. 2 showing an alternative emergencyshut-off valve assembly.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to the drawings, and initially to FIG. 1 to FIG. 3 thereof,there is illustrated a stove according to the invention, indicatedgenerally by the reference numeral 1. The stove 1 has a fuel reservoirformed by a cylindrical canister 2. A stop valve 3 is mounted at a topof the canister 2 for regulating supply of fuel gas from the canister 2through a fuel passage or supply line, indicated generally by thereference numeral 8, to an associated burner head 4. The fuel supplyline 8 has a fuel inlet 5 within the canister 2 and an outlet nozzle 9for directing fuel gas at the burner head 4. A hand wheel 6 is rotatableto move the stop valve 3 between open and closed positions, as required.An emergency shut-off valve 7 is mounted at the fuel inlet 5 of the fuelsupply line 8 and is operable when the stove 1 is knocked over to closethe fuel supply line 8. The general construction of the stove 1 islargely similar to the stove already described in WO 2008/119796 andthus for the sake of brevity does not need to be repeated here. Inaccordance with the present invention, a fuel gas emergencyover-pressure shut-off valve 10 is provided in the fuel supply line 8and is operable in response to the fuel pressure in the fuel supply line8 to close when said fuel pressure reaches a preset excess fuel pressureabove the normal operating fuel pressure.

Referring in particular to FIGS. 2 and 3, the fuel supply line 8, and inparticular the emergency over-pressure shut-off valve 10, is shown inmore detail. The emergency over-pressure shut-off valve 10 has agenerally cylindrical valve housing 11 with a through bore 12. Acomplementary valve plunger 13 is slidably mounted within the bore 12.This valve plunger 13 is movable within the bore 12 between a loweredopen position as shown in FIG. 2, and a raised closed position withinthe bore 12, as shown in FIG. 3.

When in the lowered open position, shown in FIG. 2, a bottom face 14 ofthe plunger 13 locates a small distance above a land 15 at a steppedinner end of the bore 12 which allows through passage of gas fuel. Thebore 12 has a fuel inlet 17 at an innermost end of the bore 12 whichcommunicates with the fuel canister 2 through the stop valve 3.

A fuel passage 18 extends through the plunger 13 between a plunger fuelinlet 19 and the fuel outlet nozzle 9. A sintered filter 20 is housedwithin the fuel passage 18. It will be noted that the plunger fuel inlet19 is located at a side wall of the plunger 13 which slidably engagesthe bore 12.

Resilient seals are provided at each side of the plunger fuel inlet 19,namely, an upper O-ring seal 22 and a lower O-ring seal 23. The upperO-ring seal 22 is located within a complementary circumferential groove24 adjacent an upper end of the plunger 13. Similarly, the lower O-ringseal 23 locates within a groove 25 at a lower end of the plunger 13. Theupper O-ring seal 22 engages between the plunger 13 and a wall of thebore 12 at all times forming a gas-tight seal to prevent through passageof fuel between the bore 12 and the plunger 13 to ensure that all thefuel passes through the fuel passage 18 extending through the plunger 13for delivery to the outlet nozzle 9.

A bypass recess 27 is provided in the bore 12 adjacent an inner end ofthe bore 12. The bypass recess 27 essentially comprises a generallyV-shaped circumferential channel extending around the wall of the bore12 of the valve housing 11. This bypass recess 27 cooperates with theplunger 13 to allow fuel to bypass the lower O-ring seal 23 locatedbetween the plunger fuel inlet 19 and the bore fuel inlet 17, when theplunger 13 is in the lowered open position, shown in FIG. 2. Thus, fuelcan be supplied from the fuel canister 2, through the open stop valve 3and through the open emergency over-pressure shut-off valve 10 to thenozzle 9 and burner 4 during normal operation of the stove 1. However,if the fuel pressure increases by a preset amount, for example due toheating of the canister 2, fuel pressure acting on the bottom face 14 ofthe plunger 13 will raise the plunger 13 in the bore 12 to the raisedclosed position shown in FIG. 3, in which position the lower O-ring seal23 sealingly engages with the wall of the bore 12 to prevent delivery offuel past the lower O-ring seal 23 to the plunger fuel inlet 19. In theraised position, the plunger 13 abuts against a cap 30 screwed onto anupper end 31 of the valve body 11, as shown in FIG. 3.

A resilient pressure ring 34 is mounted in an associated circumferentialrecess 35 in the plunger 13 located between the O-ring seals 22, 23 andfrictionally engages with the wall of the bore 12, being slightlyoversized relative to the bore 12. When in the lowered open positionshown in FIG. 2 the pressure ring 34 projects outwardly of the plunger13 for engagement within an associated shallow annular groove 36 in thewall of the bore 12. During normal operating conditions, the frictionalengagement of the pressure ring 34 with the wall of the bore 12, andalso because the pressure ring 34 nests in the shallow annular groove36, is sufficient to retain the plunger 13 in the lowered open position,shown in FIG. 2. However, if the fuel pressure rises significantly to apreset excess fuel pressure, for example due to heating of the canister2, the fuel pressure acting on the bottom face 14 of the plunger 13 issufficient to overcome this frictional resistance of the pressure ring34 and raise the plunger 13 in the bore 12 to the raised open positionshown in FIG. 3, shutting off fuel supply to the nozzle 9 and burner 4as previously described.

The plunger 13 comprises two parts, namely, an inner part 37 and anouter part 38 joined by a threaded connector 39 which facilitatesmounting the filter 20 in the outer part 38 and mounting the pressurering 34 in the recess 35 which is formed between the two parts 37, 38,when they are engaged. When joined together a lower end of the outerpart 38 forms a male threaded connector which projects into acomplementary female threaded socket at an upper end of the inner part37.

The stop valve 3 comprises a valve body 40 centrally mounted at a top ofthe canister 2. The valve housing 11 of the emergency over-pressureshut-off valve 10 has an outer threaded portion 42 in screw engagementwith a complementary threaded bore 43 at a top of the valve body 40. Avalve head 44 at a lower end of the valve housing 11 is engagable withan associated valve seat 45 formed at an inner end of the bore 43.Turning the valve housing 11 by means of the hand wheel 6 moves thevalve housing 11 axially in the bore 43 to engage and disengage thevalve head 44 and valve seat 45 for closing and opening the stop valve3, thus controlling the supply of fuel from the canister 2 to the burner4. A central pin 50 at the lower end of the valve housing 11 is movablethrough the fuel inlet opening 5 at an inner end of the bore 43 when thestop valve 3 is closed to disengage a ball 52 of the emergency shut-offvalve 7 as previously described in WO2008/119796.

The bore 43 of the valve body 40 is stepped having an enlarged threadedouter portion 47 which receives the valve housing 11 and a smallerdiameter smooth bored inner portion 48. The fuel inlet opening 5 isformed by a central port or a passage at an inner end of said innerportion 48 of the bore 43.

An o-ring seal 49 is mounted in an associated circumferential groove 53at a lower end of the valve housing 11 and sealingly engages between thevalve housing 11 and a wall 51 of the inner portion 48 above the borefuel inlet 17 in a gas-tight manner to ensure fuel gas must pass throughthe bore fuel inlet 17.

The cap 30 has a circular top 54 with a downwardly depending peripheralskirt 55 which threadedly engages an exterior of the upper end 31 of thevalve body 11. A circular opening 56 in the top 54 allows throughpassage of an upstanding cylindrical guide 57 at a top of the plunger13. It will be noted that a peripheral rim 58 of the opening 56 projectsinwardly of a side wall of the bore 12. An annular shoulder 59 at thetop of the plunger 13 extending around the guide 57 abuts against aninner face of the peripheral rim 58 when the plunger 13 is in the raisedclosed position shown in FIG. 3, retaining the plunger 13 within thebore 12. The opening 56 is in alignment with the nozzle 9 to allowthrough-passage of fuel gas discharged through the nozzle 9 in use.

In operation, the stop valve 3 is opened by turning the hand wheel 6 toscrew the valve housing 11 upwardly in the valve body 40. With theplunger 13 in the lowered position shown in FIG. 2 fuel gas from thecanister 2 passes through the inlet opening 5 and the valve 3 to thebore fuel inlet 17. The fuel gas then travels up through the bore 12,around the lower O-ring seal 23 via the bypass recess 27 to the plungerfuel inlet 19. Travelling through the fuel passage 18 in the plunger 13,through the filter 20 the fuel gas exits the plunger 13 through the fueloutlet nozzle 9 for burning at the burner head 4. Should the fuelpressure in the canister 2 rise by an unacceptable amount, due forexample to heating of the canister 2, then the fuel pressure acting onthe bottom face 14 of the plunger 13 moves the plunger 13 upwardly inthe bore 12, overcoming the frictional resistance of the pressure ring34, to the raised cut-off position shown in FIG. 3, the seal 23 cuttingoff fuel supply to the burner 4 as it moves upwardly out of the bypassrecess 27. The emergency over-pressure shut-off valve 10 can be resetwhen the fuel pressure in the canister 2 has dropped back to normal.Re-setting the emergency over-pressure shut-off valve 10 to the openposition is simply achieved by manually pushing the plunger 13 back downthe bore 12 into the lowered normal operating open position wherein theseal 23 again locates at the bypass recess 27 as shown in FIG. 2.

Referring to FIG. 4 there is shown another emergency shut-off valve 60according to the invention. In this case a spring 61 is mounted in thevalve housing 11 to engage and urge the plunger 13 towards the openposition. This spring 61 may be provided instead of or in addition tothe resilient pressure ring 34.

The invention is not limited to the embodiments hereinbefore describedwhich may be varied in both construction and detail within the scope ofthe appended claims.

1. A stove, including: a burner, a fuel reservoir, a fuel supply linecommunicating between the fuel reservoir and the burner, a stop valve inthe fuel supply line which is operable to control the supply of fuelfrom the fuel reservoir to the burner, and a normally open emergencyshut-off valve in the fuel supply line which is operable to close thefuel supply line, wherein said emergency shut-off valve is operable toclose the fuel supply line in response to the fuel pressure in the fuelsupply line, when said fuel pressure reaches a preset excess fuelpressure above a preselected normal operating fuel pressure.
 2. Thestove as claimed in claim 1, wherein the emergency shut-off valveincludes: a valve housing having a through bore, a complementary valveplunger slidably mounted in the bore, said valve plunger being movablerelative to the bore between an open position and a closed position,said valve plunger cooperating with the bore such that, in the openposition, a fuel passage through the bore is provided and in the closedposition, fuel flow through the bore is prevented.
 3. The stove asclaimed in claim 2, wherein: the bore has a bore fuel inletcommunicating with the fuel reservoir, the valve plunger has a fuelpassage extending through the valve plunger with a valve plunger fuelinlet and terminating in a fuel outlet nozzle, said valve plunger fuelinlet being provided at a side wall of the valve plunger which slidablyengages the bore, resilient seals being provided at each side of thevalve plunger fuel inlet which are engagable between the valve plungerand the bore to prevent through passage of fuel between the bore and thevalve plunger, a fuel bypass recess in the bore which cooperates withthe valve plunger to allow fuel to bypass the resilient seal locatedbetween the valve plunger fuel inlet and the bore fuel inlet when thevalve plunger is in the open position.
 4. The stove as claimed in claim2, wherein retaining means is provided for retaining the valve plungerin the open position, when the fuel pressure is below said preset excessfuel pressure.
 5. The stove as claimed in claim 4, wherein the retainingmeans comprises a resilient pressure ring mounted in a circumferentialrecess in the plunger and frictionally engaging with the bore.
 6. Thestove as claimed in claim 4, wherein the retaining means projectsoutwardly of the plunger for engagement within an associated annulargroove in the bore when the plunger is in the open position.
 7. Thestove as claimed in claim 4, wherein the retaining means is a springmounted in the valve housing and engaging and urging the valve plungertowards the open position.
 8. The stove as claimed in claim 2, wherein afuel filter is mounted within the fuel passage in the valve plunger. 9.The stove as claimed in claim 2, wherein a cap is mounted at an outerend of the through bore, said cap being engagable with the valve plungerwhen said valve plunger is at the outer end of the through bore toretain the valve plunger within the through bore, said cap having anopening therein in alignment with the fuel outlet nozzle to allowthrough-passage of fuel gas discharged from the nozzle in use.
 10. Thestove as claimed in claim 5, wherein the valve plunger comprises aninner part and an outer part joined by a threaded connector, a lower endof the outer part forming a male threaded connector for engaging with acomplementary female threaded socket formed at an upper end of the innerpart, said recess for reception of the pressure ring being formedbetween said parts when they are engaged.
 11. The stove as claimed inclaim 2, wherein the stop valve comprises a valve body mounted at a topof the canister, the valve housing of the emergency shut-off valvehaving an outer threaded portion in screw engagement with acomplementary threaded bore in the valve body, a valve head at a lowerend of the valve housing being engagable with an associated valve seatformed at an inner end of the bore at an outlet end of a fuel inletopening communicating with the fuel reservoir.
 12. The stove as claimedin claim 11, wherein said bore is stepped having an enlarged threadedouter portion which receives the valve housing and a smaller diametersmooth bored inner portion, the fuel inlet opening being formed by aport at an inner end of said inner portion, a seal being mounted in anassociated circumferential groove at a lower end of the valve housingsealingly engaging between the valve housing and a wall of the innerportion above the bore fuel inlet in a gas-tight manner to ensure fuelgas must pass through the bore fuel inlet.